Bar & pie charts: Quantitative Aptitude Notes for JEST

Bar & Pie Charts – Quick Study Guide

(Quantitative Aptitude – JEST)

1️⃣ Simple Explanation

Chart	What It Shows	When to Use
Bar Chart	Quantitative comparison of discrete categories (e.g., sales by month, student scores by subject).	When you need to compare exact values or see differences at a glance.
Pie Chart	Proportion of each category to a whole (percentages that sum to 100 %).	When you need to show how parts make up a whole (market share, budget allocation).

Both charts are visual tools that help you answer questions like:

Which category is largest?
What is the percentage share of a category?
How many units are missing from a list?

2️⃣ Key Points

2.1 Bar Charts

Feature	Detail
Axes	X‑axis = categories, Y‑axis = numeric values.
Bars	Height (or length) is proportional to the value.
Missing Data	If a bar is missing, its value is zero unless stated otherwise.
Units	Read from the Y‑axis tick marks.
Comparisons	Compare bar heights or lengths directly.
Common Questions	Which is highest/lowest? What is the difference between two bars? What is the total?

2.2 Pie Charts

Feature	Detail
Whole	The circle = 100 %.
Slices	Each slice’s angle is proportional to its value.
Percentage	`slice % = (slice value / total) × 100`.
Missing Slices	If a slice is not shown, its share is 0 % (unless “others” is combined).
Labeling	Usually shows either the percentage or the absolute value.
Common Questions	What is the percent of a slice? Which slice is largest? What is the value of the missing slice?

2.3 General Tips

Check the legend – it tells you what each bar/slice represents.
Look for “others” categories – this usually means “all remaining values combined.”
Use the total – for pie charts, if you know one slice’s percent, you can find the rest.
Convert to fractions – useful when percentages are not provided.
Round carefully – keep two decimal places unless the problem specifies otherwise.

3️⃣ Worked Example

3.1 Bar Chart Example

Problem
A bar chart shows the monthly sales (in ₹) of a shop for January‑March:

January: ₹12,000
February: ₹9,600
March: ₹15,200

Questions:
a) What is the total sales for the quarter?
b) Which month had the highest sales?
c) What is the difference between February and March sales?

Solution

Month	Sales (₹)
Jan	12,000
Feb	9,600
Mar	15,200

a) Total sales
[ 12{,}000 + 9{,}600 + 15{,}200 = 36{,}800 \text{ ₹} ]

b) Highest sales month
March (₹15,200) is the tallest bar → highest sales.

c) Difference (Mar – Feb)
[ 15{,}200 - 9{,}600 = 5{,}600 \text{ ₹} ]

3.2 Pie Chart Example

Problem
A pie chart shows the distribution of a city’s population (in thousands) across four districts:

North: 40 %
South: 25 %
East: 20 %
West: missing slice

If the total population is 500 000 people, find:
a) The population of the West district.
b) The absolute number of people in the East district.

Solution

Let total population (T = 500{,}000) (thousands → 500).

Find missing percentage
[ \text{Sum of given percentages} = 40 + 25 + 20 = 85% ] [ \text{Missing percent} = 100 - 85 = 15% ]
West population
[ \text{West} = 15% \times 500 = 75 \text{ thousand} ]
East population
[ \text{East} = 20% \times 500 = 100 \text{ thousand} ]

Answer

West district: 75 000 people.
East district: 100 000 people.

4️⃣ Quick Revision Summary

Topic	Key Takeaway
Bar Chart	Height of bar = value; compare heights for largest/smallest; sum values for totals.
Pie Chart	Whole = 100 %; slice % = (value / total) × 100; missing slice = 100 % minus sum of shown slices.
Reading	Always note units on axes; look for legends and labels.
Missing Data	Absence of a bar or slice usually means zero, unless “others” indicates a combined category.
Common Calculations	Total, difference, percentage share, missing value.
Tip	Convert percentages to fractions when the total is unknown; keep two decimal places when necessary.

Practice Tip:
Draw a quick bar chart or pie chart for a familiar set of data (e.g., your own monthly expenses) to reinforce these concepts.

Happy studying!